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Toxicity to microorganisms

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Description of key information

In an activated sludge guideline study Modified Small Vinyl Ester did not inhibit respiration of waste water bacteria at a loading rate of 100 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
100 mg/L

Additional information

The influence of Modified Small Vinyl Ester on the respiration rate of activated sludge was investigated after a contact time of 3 hours. The study procedures described in this report were based on the OECD guideline No. 209, 1984. In addition, the procedures were designed to meet the test methods of the Council Regulation (EC) No. 440/2008 of 30 May 2008, Publication No. L142, Part C11 and ISO Standard 8192 (2007). The tested batch of Modified Small Vinyl Ester was a clear light yellow-greenish to light brown, highly viscous liquid. It was indicated to be light sensitive. To facilitate handling, Modified Small Vinyl Ester was heated to 50 °C for 95 minutes. Modified Small Vinyl Ester was weighed on a thin glass slide and thereafter added to the test bottles. Weighing was performed under dimmed light and transferred to the testing chamber using bottles covered by aluminium foil. Since Modified Small Vinyl Ester was hardly soluble in water, test concentrations were prepared separately in Milli-RO water. Two 1-litre test bottles were filled with 250 ml of test substance mixtures with initial loading rates of 200 mg/l. The mixtures were stirred in closed dark brown bottles for 26 hours. Subsequently, 16 ml synthetic sewage feed, 200 ml sludge and Milli-RO water up to 500 ml were added resulting in a loading rate of 100 mg/l. This loading rate was tested in duplicate. Two controls without Modified Small Vinyl Ester were tested in each test series. Optimal contact between the test substance and test medium was ensured applying continuous aeration and stirring during the 3-hour exposure period. Thereafter, oxygen consumption was measured and recorded for approximately 10 minutes. No significant inhibition of respiration rate of the sludge was recorded at a loading rate of 100 mg Modified Small Vinyl Ester per litre. The duplicate measurement confirmed the result of the first measurement. Therefore, no further testing was needed. Hence, the EC50 of Modified Small Vinyl Ester exceeded a loading rate of 100 mg/L.

It is concluded that under the conditions of the present test, Modified Small Vinyl Ester was not toxic to waste water (activated sludge) bacteria at a loading rate of 100 mg/L.